This invention relates to a device for performing a function test on thermographic apparatus.
Thermographic apparatus serves to detect a target by responding to differences in the temperature of the target and the temperature of the surroundings of the target. Various forms of thermographic apparatus are known in the art, and the present invention may be used with various forms or kinds of such apparatus. An example of one form of thermographic apparatus with which the present invention may be used is the apparatus disclosed in Federal Republic of Germany Offenlegungsschrift No. 1,772,312 of H. Siebecker et al., filed Apr. 27, 1968 and published Dec. 10, 1970, and the corresponding British patent No. 1,242,162 of Eltro GmbH, filed Feb. 18, 1969 and published Aug. 11, 1971. The disclosures of these documents are incorporated herein by reference.
Known thermographic apparatus, such as the apparatus described in the above mentioned German and British documents, typically include an infrared (IR) optical system, a scanning prism, a row of detectors, and an evaluation electronic system which forwards the received signals to a row of light-emitting diodes arranged behind the row of detectors. The rays coming from the light-emitting diodes can be used to produce an IR image on an image screen.
For the military use of thermographic apparatus, it is necessary to have an easy way of checking the operation of the apparatus. When thermographic apparatus is placed in operation, a simple function test can be performed. From the IR picture produced, it can be noted whether the thermographic apparatus is operating properly. However, if the thermographic apparatus is installed on a vehicle such as an airplane or a tank which is located in an enclosure such as an airplane hangar or a shed, and if the thermographic apparatus on the vehicle is pointed at a relatively flat surface or "structureless" surface such as a door or a wall, then a satisfactory functional operational test can not be made in the conventional or normal way because a uniformly bright surface appears on the image screen, and it can not be noted from this image whether the thermographic apparatus is operating properly or not.
It is the object of the present invention to overcome this difficulty, and to provide a simple, effective, and inexpensive arrangement whereby a simple function test of the thermographic apparatus can be quickly made, to answer the question whether the apparatus is operating properly, yes or no, in all situations, including the situation described above where the thermographic apparatus is pointed toward a door or wall or other structureless surface.